Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with agraphical user interface showing a first embodiment of the new design;and,

FIG. 2 is a second embodiment thereof.

The broken line showing of the display screen and all other broken linesshowing portions of the graphical user interface are included forpurposes of illustrating portions of the article and form no part of theclaimed design.

CLAIM The ornamental design for a display screen or a portion thereofwith a graphical user interface, as shown and described.